Method for covering press rolls



Sept. 8, 1970 "K. K.N|KKANEN 3,526,939

v I METHOD FOR COVERING PRESS ROLLS 2 Sheets-Sheet 1 TA INL E55 ATTORNEY.

United States Patent O r 3,526,939 METHOD FOR COVERING PRESS ROLLS Klaus Kalevi Nikkanen, Karhula, Finland, assignor to A. Ahlstrom Osakeyhtio, Karhnla, Finland, a corporation of Finland Continuation-impart of application Ser. No. 587,732, Oct. 19, 1966. This application Dec. 19, 1968, Ser. No. 785,318

Int. Cl. B21d 53/26 U.S. Cl. 29-1484 14 Claims ABSTRACT OF THE DISCLOSURE Press roll bodies are covered by applying a weldable, relatively thick, metallic jacket to a roll body, locally applying high temperatures to the jacket to render a surface layer thereof molten and thereby shrink the jacket to the roller body, and machining at least the resulting fused layer from the jacket to provide a press roll cover having an essentially 'homogenous structure.

CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my copending application for United States letters Patent Ser. No. 587,732, filed Oct. 19, 1966, and now abandoned.

FIELD OF THE INVENTION This invention relates to a method for covering press rolls; More particularly, this invention relates to the application of metallic jackets to non-weldable press roll bodies so as to provide press rolls suitable for removing liquid from a liquid-containing web material.

BACKGROUND OF THE INVENTION Press rolls are commonly employed for the dewatering of paper webs and felts in papermaking machiens. Pulp mills employ wet press machines for the removal of water from the pulp by passing it through a pair of rolls mounted in a high pressure press. The employment of grooved rolls in such press assemblies is highly desirable. Such press rolls are provided with generally circumferential grooves throughout the entire periphery of the roll. The grooves can be on the order of about 2.5 millimeters deep and this facilitates removal of the water from the pulp at the press nip. Additionally, the grooves are vented to the surrounding atmosphere so that water flow into the grooves is not impeded by any pressure build up.

The grooved surface of the roll is exposed to both high pressures and corrosive conditions. Such severe conditions of wear and tear on the grooved surface necessitate the machining of new grooves into the surface of the roll relatively often. However, such machining gradually reduces the roll diameter until it is too small to be suitably employed in the dewatering operations. In view a of the high pressures that are encountered in effective dewatering operations, the diameter and wall-thickness of the rolls must be great. Also, non-corrosive metals must be employed in the roll because of the corrosive conditions encountered. Accordingly, the replacement of such rolls is quite expensive.

In the past, the production of such rolls has sometimes been achieved by making the whole roller out of a high grade steel alloy such as stainless steel. However, this has been a most expensive manner of proceeding. In addition to expense, the manufacture of press rolls by conventional techniques, such as casting, presents inherent difliculties in the production of grooved press rolls therefrom. For example, cast rolls are difficult to machine, since the metallic structure of the resulting roll is not homogeneous, but contains hard spots, pores and other 3,526,939 Patented Sept. 8, 1970 defects. This lack of desired machinability renders cast rolls unsuitable for making grooved rolls, particularly if the grooves are to be deep and narrow.

Some efforts have been made to apply surface coverings to inexpensive roller bodies such as those made out of cast iron. Cast iron, however, being a non-weldable material, does not lend itself to the ready affixing of an outer covering having a suitable working surface, e.g. stainless steel, thereon, since the covering cannot be welded to it. To overcome this problem, there have been suggestions for applying an outer layer by winding it on, by winding it over an intermediate tube, by providing an insert of weldable material in the cast iron roller body and welding the formed tube to it, as well as in various other ways which are complicated and expensive and have not provided a real solution to the problem.

Accordingly, it is an object of the present invention to provide press rolls by a simple and relatively inexpensive method.

It is a further object of the invention to provide a method for covering press roll bodies wherein the roll body is made of a non-weldable metal.

Another object of the inventon is to provide a method for producing press rolls having a relatively thick surface layer of homogeneous structure, which is suitable for the manufacture of grooved rolls.

Another object of the invention is to provide a method for producing press rolls that can be suitably employed as grooved rolls under high pressures.

A still further object of the invention is to provide press rolls suitable for use in operations that require high durability and resistance to corrosion.

SUMMARY OF THE INVENTION The foregoing and other objects of the invention are achieved by the present invention wherein a method of covering a relatively thick-walled, substantially cylindrical press roll body having a relatively smooth surface is provided, which method comprises the steps of:

(A) Providing a metallic jacket on the cylindrical surface of the press roll body;

(B) Applying heat to a selected point on the jacket in an amount suflicient to fuse a portion of said jacket in an outer layer thereof;

(C) Continuously moving said heat from said selected point to other points on the exterior surface of said jacket to form a fused outer layer and thus create a substantially continuous intimate contact between said jacket and said press roll body; and

(D) Machining the jacket to remove at least said fused outer layer and provide a surface layer in said jacket having a homogeneous structure.

In this manner, a press roll having a relatively thick, homogeneous jacket is provided by a method that is relatively simple and inexpensive. Unlike cast press rolls, the press roll of the present invention may be machined to provide deep, narrow grooves in the homogeneous outer layer thereof.

The present invention has particular applicability when the body of the press roll is made of a non-weldable material, such as cast iron. The surface of the jacket is rendered molten by the local application of intense heat. As discussed hereinafter in more detail, the jacket is plastically deformed and forced against the surface of the roller body at the point of local heating, while at the same time, lateral expansion of the jacket is restricted by the surrounding parts of thejacket. Upon cooling, the jacket contracts into intimate contact with the underlying roller body. The resulting jacket fits onto the roller body sufficiently tight that the fused outer layer of the jacket and any underlying heterogeneous portions of the jacket can be machined away to provide a relatively homogeneous surface. The surface of the resulting press roll can be satisfactorily machined and employed without failure as a grooved or other type of press roll in a press assembly under high operating pressures.

In addition, the method of the present invention is not limited to the production of new press rolls, but is applicable to the repair of worn or damaged rolls, particularly when expensive, non-corrosive surfaces, e.g., stainless steel, are required. Since the bearings, bearing cap, journals and main body of the Worn or damaged press rolls are still in working condition, the present invention provides a method of repairing such rolls and making them serviceable once again in a simple and inexpensive manner.

According to one aspect of the present invention, the local application of heat to the surface of the jacket so as to cause shrinkage of the jacket to the roller body is provided by applying a single circumferential bead of Weld material to the surface of the jacket in a manner such that a substantially continuous, cylindrical, fused outer layer of weld and jacket material is provided around the jacket.

According to another aspect of the present invention, the locally applied heat for fusing the outer surface of the jacket is provided by means of a direct high temperature source, such as a plasma jet generator, a LASER generator, and the like.

The method of the present invention provides a relatively thick, homogeneous jacket at relatively low costs.

BRIEF DESCRIPTION OF THE DRAWINGS Further features of the invention will become apparent from the following description in detail in conjunction with the accompanying drawings.

FIG. I is a perspective view showing a preferred means of providing the jacket according to the present invention;

FIG. 2 is a side elevation partly in diagrammatic showing the circumferential welding of the jacket shown in FIG. 1 according to one aspect of the present invention;

FIG. 3 is an enlarged fragmentary sectional view of a press roll formed in the manner of FIG. 2;

FIG. 4 is a side elevation, partly, diagrammatic showing the application of the plasma jet flame to the jacket of FIG. 1 according to another aspect of the invention;

FIG. 5 is an enlarged fragmentary sectional view of a press roll formed in the manner shown in FIG. 4;

FIG. 6 is an enlarged fragmentary sectional view illustrating the effect of the heating of the invention in the securing of the outer tube on to the inner core or body showing the condition of the press roll that is existing while the heat is fully effective; and

FIG. 7 is a view similar to FIG. 6 showing the condition of the press roll after the heated section has cooled.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, a body portion 10 of a roll 12 is composed of non-weldable cast iron and is cast or otherwise formed into a substantially cylindrical shape of the size desired. The body portion 10 has an axle portion 14 integral therewith. A jacket 16 is provided about the circumferential surface of the body 10, which jacket is composed of a weldable, preferably corrosion-resistant metal, such as austenitic stainless steel, bronze, titanium, aluminum alloys and the like. In the embodiment shown, the jacket 16, as illustrated, consists of three pieces of stainless steel plate 16a, 16b, and 160. While the jacket is illustrated as being formed from a plurality of plates or shells, it may be formed in any suitable manner. For example, a preformed tube of metal may be telescopically fitted over the roll body 10, or a single plate may be fitted around the roll body and longitudinally welded along a single joint to form a tube. The jacket may be, for example, between about 0.15 and about 1.50 inches thick, preferably between about 0.25 and about 1.0 inch thick.

To assemble the jacket 16, each of the plates 16a, 16b, and 160 may be bent, fitted onto the body 10 and then 4 strapped thereto with draw bolts. The roll body 10 is provided with a relatively smooth surface. The term relatively smooth as employed herein is meant to include a surface which is at-least as smooth as that obtained by precision casting or normal turning.

The longitudinal joints 18a, 18b, and are preferably staggered, as shown, and may be tack-welded in order to hold the meeting edges of the cylindrical plates 16a, 16b, and 16c together. Likewise, the transverse joints 20 and 22 may be tack-welded. Optionally, the jaws of a hydraulic press (not shown) may be suitably employed to force the cylindrical plates 16a, 16b, and 16c into intimate contact with the roll body 10 while the various joints are tack welded. These joints are by no means intended to serve as a weld to hold the jacket 16 onto the roll body 10, but merely serve to hold the edges of the plates forming the jacket together in order to complete the jacket. As the weld metal cools, it draws the stainless steel plates into intimate contact with the relatively smooth surface of the roll body 10 to some extent.

Referring now to FIG. 2 an aspect of the present invention is shown wherein heat is locally applied to the jacket 16 by means of a spirally applied molten weld material from a welding rod or electrode 24 from the welding head 26. The weld material, which may be stainless steel, bronze, low carbon steel, or the like, is applied circumferentially about the jacket 16 employing, for example, the head 26 as a motor-driven traveling head which is driven by conventional means (not shown). Various welding techniques may be employed. However, it is preferred to employ submerged arc welding equipment, i.e., where the welding bead is formed under a blanket of flux material. The welding machine is preferably above the roll body as to travel at the desired slow speed longitudinally of the roll body while the roll is being rotated at the desired relatively slow speed. Thus, though the action is actually a continuous one, it is slow enough that it can be considered as being accomplished in small increments.

The local application of heat by means of welding as shown in FIG. 2, is suflicient to cause the formation of a fused outer layer 28 which comprises weld material and jacket material. When the jacket material is stainless steel, for example, the heat is sufficiently intense to form an underlying, heterogeneous layer, wherein permanent microstructural changes occur. It is preferred that the bead-foming weld material be the same material as is the jacket 16. For example, if the jacket 16 is stainless steel, it is preferred that the weld electrode be formed of stainless steel as well. However, a material different from that of the jacket 16 may be utilized, if desired. Upon cooling, the contraction of the fused surface layer 28 causes shrinkage of the jacket 16 to the body 10, thereby graiwing the jacket into intimate contact with the roll Referring now to FIG. 3, an enlarged fragmentary view of a press roll formed in the manner shown in FIG. 2 is shown. As previously mentioned, the thickness of the jacket 16 may be in the range of between about 0.15 and about 1.5 inches, preferably between about 0.25 and about 1.0 inch. The thickness of the weld layer 28 may be, for example, between about and about of an inch. The fused outer layer 28 is formed at a temperature that is greater than the melting temperature of the weld material 24 and is, for example, in the case of a stainless steel jacket, about l500 C. The press roll 12 is slowly rotated while molten weld material 24 is applied to the surface of the jacket 16 and a slow spiral of weld material is deposited.

As previously mentioned in the case of a stainless steel jacket, for example, the high temperatures employed in the welding operation cause permanent microstructural changes in an underlying layer 30 in the jacket 16. These microstructural changes in the metal jacket may be viewed as causing the formation of a continuous heterogeneous underlying layer 30 within the periphery of the jacket 16 and adjacent the outer, fused layer 28. As will be hereinafter described, the fused layer 28 and any underlying layer 30 containing permanent microstructural changes are removed by machining to provide a homogeneous surface layer in jacket 16. If the non-homogeneous underlying layer 30 and outer layer 28 were not removed from the press roll 12, i.e., if only the outer layer 28 or a portion thereof were removed, satisfactory grooved rolls could not be produced. As previously indicated, a nonhomogeneous jacket is not suitable for the machining of deep, narrow grooves.

. Referring now to FIG. 4, another aspect of the present invention is illustrated wherein the jacket 116 is intensely heated into intimate contact with the relatively smooth surface of the press roll body, by the local application of a direct high temperature heat source, such as a plasma jet generator 126. The utlization of a plasma jet generator is only exemplary of this aspect of the present invention. Thus, any direct high temperature heat source may be employed, such as an electric arc welding gun, a gas welding nozzle, a Laser generator, and the like. The term direct heat source" is employed herein in contradistinction to the indirect application of heat to the surface of the jacket via the melting of a welding rod to create a fused layer of material around the jacket.

The plasma jet generator is conventional equipment in which an electric arc is employed for heating a gaseous material, with the electric are being stabilized by having the gaseous material to be heated pass through the plasma jet generator continuously. The gas that is passed through the plasma jet generator may be argon, nitrogen, hydrogen, carbon dioxide, etc. However, argon is the preferred gas for the purposes of the present invention.

The plasma jet generator is capable of producing extremely high temperatures, and can be employed to heat the jacket 116 to a temperature above the melting point of the jacket material. A preferred heating temperature in the case of a stainless steel jacket, for example, in this aspect of the invention is about 1500= C.

Regardless of the mode of heating utilized, the temperature employed will, of course, depend upon the melting point of the particular jacket material and weld material, if the welding aspect of the invention is utilized. Thus, if the jacket or weld material is titanium (1800 C. M.P.), bronze (900 C. M.P.), a suitable tempera: ture is selected above the melting point (M.P.) of the particular metal to render the surface of the metal molten or fused.

Two types of plasma jet generators are conventionally employed, viz., a transferred and a non-transferred type, and either type is suitable for use in the present invention. In the non-transferred type of plasma generator, the positive and negative electrodes are contained within the generator, itself. Thus, a conventional non-transferred type of plasma generator contains a negative electrode with an annular positive electrode and the gaseous medium, e.g. argon, flows longitudinally between the electrodes. In the transferred type of electrode, the nega' tive electrode is contained within the plasma generator, while the positive electrode is the workpiece (in this case the press roll) itself. The transferred plasma jet generator is preferred for use in the present invention, although either type of plasma jet generator is suitable.

As in the case of the welding aspect of the invention, the direct heat source, e.g., plasma jet generator, may be employed by rotating the press roll and utilizing a motor-driven traveling plasma generator 126 so that the plasma flames 127 are applied to surface of the jacket 116 in a circumferentially, continuous manner. For example, the path followed by the flames 127 may be a continuous, but very slow, spiral. The application of the plasma flames to the jacket 116. causes the formation of a molten or fused outer layer 128 in the jacket, which may have a melting depth, for example, of between about and about of an inch or more, if desired. At any rate, the melting depth should be suflicient to cause the desired shrinkage of the jacket 116 to the body of the press roll 112.

As in the case of the aspect of the invention illustrated in FIG. 2 of the drawings, the application of the plasma jet flames to the jacket in a local manner as in this aspect of the invention, can cause the formation of a nonhomogeneous underlying layer, wherein permanent microstructural changes occur, in a stainless steel jacket 116, for example. This is illustrated in FIG. 5 which is an enlarged fargmentary cross-section of a press roll formed in the manner shown in FIG. 4. Thus, a molten or fused outer layer 128 is depicted, which layer is formed in the jacket 116 by application of the plasma jet flames. Also, permanent metallic microstructural changes have taken place below the outer layer 128 in the underlying layer 130. As before, the application of intense heat in a local manner, as described, creates intimate contact between the jacket 116 and the relatively smooth surface of the roll body along the surface 132. For the reasons previously indicated, the fused outer layer 128 and any non-homogeneous underlying layer 130 containing permanent microstructural deformation must be removed in order to obtain a homogeneous press roll working surface.

The direct heat source aspect of the present invention is preferred, with the plasma jet generator form thereof being especially preferred, since it eliminates the need for any consumable welding electrode. Also, since better penetration of heat is possible, a thicker jacket may be utilized than is possible with the indirect Welding heat application embodiment of the present invention.

The local heat of fusion may be applied to the surface of the jacket in any suitable manner. Although the foregoing description has been directed toward the application of a single circumferential bead of weld material around the jacket in a slow spiral or the application of the heat from a plasma gas generator, Laser genertor, etc., in a like manner, the present method is not so limited. Any suitable means of heat application may be employed. Thus, for example, a plurality of axial beads of weld material, one beside the other, may be applied longitudinally along the surface of the press roll jacket to provide the necessary intense heat. Likewise, the application of the direct heat source, i.e., plasma flames, etc., may be conducted in a similar manner, viz., axially, along the surface of the jacket in order to melt the surface layer thereof.

Any suitable machining operation may be employed for the removal of the fused outer layer of the jacket and any adjacent underlying heterogeneous layer that may result from the melting operation such as occurs when the jacket is made of stainless steel. Thus, machining methods, such as turning, grinding, milling, and the like or, for example, electrochemical methods, which do not themselves cause microstructural changes in the jacket may be employed to provide a jacket having a surface layer of homogeneous structure.

The amount of metal to be removed during the machining operation will depend upon the depth of nonhomogeneous metal in the jacket. Thus, the fused or molten, non-homogeneous surface layer of the jacket is always removed. In addition, as previously mentioned, the intense heating may cause the formation of an underlying layer beneath and adjacent the surface layer that is non-homogeneous, i.e., contains hard spots, pores or other defects, and contains permanent microstructural changes in the metal. The existence of such defects may be easily determined, experimentally, by means of an electron microscope, for example. In such instances, the nonhomogeneous underlying layer is also removed to provide a jacket having an essentially homogeneous structure. For example, if an original stainless steel jacket is about one inch thick and a layer of welded molten material inch thick is deposited thereon, at least a total of A; to 7 inch of metal should be machined from the press roll by means of turning, for example, to provide a surface layer of homogeneous structure. The foregoing is only exemplary, but as a practical matter, about A to inch of metal are generally removed during the machining operation regardless of which aspect of the invention is employed, viz., welding, plasma gas generator, Laser generator, and the like.

It is not intended to limit the present invention to any particular theory. However, the following discussion is presented as a possible explanation of the operation of the present invention. Referring now to FIG. 6, intense heat from a heating element (not shown) is being applied to the outer surface 214 of the jacket 216 at a temperature sufficient to render surface 214 molten, and cause the increment 215 of the stainless steel material, for example, under the heating element to expand in response to the application of the heat. The intense heat may be provided indirectly, i.e., by welding, or directly, e.g., by a plasma jet generator. Sideways expansion, however, in the direction of the arrows 217 and 218 is of little moment for it is resisted by the whole body of the jacket 216. Expansion upward and downward, however, as shown by the arrows 219 and the upward bulge 220 takes place more readily. Obviously, the material can expand outwardly as shown at 220 since there is nothing but the molten weld metal or direct heat being applied to it to prevent it from expanding.

Downward expansion as shown by the arrows 219 and by the downward bulge 221 is possible to some extent. However, when the jacket 216 is initially placed over the roll body 210, it is not possible to eliminate all of the space between the inner surface 222 of the jacket 216 and the outer surface 223 of the roll body 210 by the bending action employed. The presence of air and the inability to form a tight fit assures the existence of this space. Thus, the increment 215 expands downwardly as seen at 221 and tightly fills the space.

As the heating element moves on, the increment 215, as seen in FIG. 7, cools off, the upward bulge disappears so that the upper surface 225 of the increment is substantially restored to the same level as the outer surface 214 of the jacket 2.16. The sideways expansion, though limited in extent, results in retraction as seen by the arrows 226 and 227. Although the downward bulge 221 retracts to some extent as shown at 228 and by the arrows 229, it still occupies the space that existed between the surface 222 of the tube and the surface 223 of the roll body and tightly engages the surface 223 of the roll body. This is due to the fact that only a localized area, or increment, is heated at a time and cools relatively slowely. During that cooling, the surface part of the tube surrounding the localized area, which has expanded and has partially been forced away as the heated area expands now contracts in the direction shown by the arrows 230 and 231 in FIG. 7. This contraction of the increment itself at 225 forces the metal underlying the layer 225 radially inwardly. Hence, the bottom 228 of the increment tightly engages the roll surface 223.

Inasmuch as the longitudinal movement of the heating means and the rotational movement of the press roll causes the incremental heating action to take place throughout the whole of the jacket, and thus over the whole of the outer surface of the roll body, the jacket 2:16 is shrunk onto the body and engages it tightly without any extraneous fastening means. The resulting press roll will perform effectively when employed in its particular industrial application and can be machined to provide a homogeneous surface.

The following examples are presented to illustrate the practice of the present invention in the production of press rolls.

Example 1 A cast iron roll body is turned down to a diameter of 670 millimeters and to a relatively smooth surface finish.

A stainless steel jacket is formed onto the cast iron body from three stainless plates that are each about 3 feet wide and 4 inch thick. Each is bent, fitted onto the roll and is strapped fast thereto with draw bolts. The longitudinal and transverse joints are tack-welded.

Next, the entire jacket is welded by submerged arc welding, circumferentially in a slow spiral. An electrode having a 4 millimeter diameter is employed with a 550 a. welding current, an arc voltage of 38 v., and a travel speed of 23.3 inches per minute. The welding is accomplished by mounting the welding machine on a column and boom, while the press roll is placed on a motor driven roller bed with continuous speed regulation. When the roll is rotating at a peripheral speed equal to the welding speed, the boom with automatic welding machine is advanced at a speed such that the spiral formed surface weld is obtained.

One hundred kilograms of electrode and kilograms of powder are required to circumferentially cover the entire stainless jacket. The welding time is 20 hours. The depth of the profile between adjacent beads is about Vs inch.

After welding, the roll is turned and ground down to remove about 7 inch of material. Grooves are machined on a lathe having depth of 2.5 millimeters. The stainless jacket is tight and a good finish is obtained.

The grooved roll as obtained above is placed in use in a pulp mills high pressure press and subjected to a linear pressure of about 350 kilopounds per centimeter. The roll is fully equal to rolls of stainlesss cast steel, but is, of course, much less expensive, since only 15 to 20 percent of the total weight of the roll is expensive stainless steel, for example, 18/8 steel. The remainder of the roll is cast iron, which is much less expensive than stainless steel.

Example 2 The procedure of Example 1 is repeated, except that instead of applying spiral shrinkage welds about the circumference of the tack-welded stainless jacket, a plasma jet generator head is substiituted for the welding head on the automatic welding machine. It should be noted that the same equipment, i.e., electric arc welding nozzle, plasma jet generator, etc. can be used when melting a welding rod to create a fused layer of weld and jacket material around the jacket, or to melt the surface layer of the jacket to create a layer of fused material around the jacket. The boom is automatically advanced while the roll is rotated, so that the flame from the plasma generator form a molten spiral path around the periphery of the roll. The plasma jet generator is operated with an argon medium and a temperature of about 1600 C. is applied to the stainless jacket. A melting depth of about 7 inch results.

The resulting roll is turned and ground as before to remove about A; inch of metal from the surface of the layer. Grooves are machined on a lathe as before and the resulting jacket is tight and a good finish is obtained.

In addition, a wide variety of jackets may be employed in the method of the present invention, so long as the jacket is corrosion resistant, durable and Weldable. Thus, titanium, bronze, aluminum alloys and the like may be employed.

The foregoing examples are intended to illustrate various modes of practicing the present invention. It will be obvious that slight modifications in materials, procedure and equipment may be made without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A method of covering a relatively thick-walled, substantially cylindrical press roll body having a relatively smooth surface, which method comprises the steps of (A) providing a weldable, metallic jacket on the cylindrical surface of said press roll body, said jacket being of metal which cannot be suitably fused directly to said body;

(B) applying heat to a selected point on the exterior surface of said jacket in an amount sufficient to fuse a portion of said jacket in an outer layer thereof; (C) continuously moving said heat from said selected point to other points on the exterior surface of said jacket to form a fused outer layerv and thus shrink said jacket and create a substantiallycontinuous intimate contact between said jacket and said press roll body; and (D) machining said jacket to remove at least said fused outer layer and provide a surface layer in said jacket having a homogeneous structure.

2. The method of claim 1 wherein the heat is provided by applying a single circumferential head of weld material around the jacket in the form of a slow spiral.

3. The method of claim 1 wherein the surface layer is formed from a plurality of axial beads of weld material, one beside the other. 1

4. The method of claim 1 wherein the heat is provided by a direct heat source.

5. The method of claim 4 wherein the heat is provided by means of a high temperature plasma jet flame.

6. The method of claim 1 wherein an underlying layer having a heterogeneous structure of substantial thickness is formed in said jacket adjacent said outer layer, said underlying layer being removed to provide a surface layer in said jacket having a homogeneous structure.

7. The method of claim 6 wherein said jacket is stainless steel.

8. The method of claim 1 wherein said jacket has an initial thickness in the range of between about 0.15 and about 1.50 inches.

9. The method of claim 8 wherein said jacket has an initial thickness in the range of between about 0.25 and about 1.25 inches.

10. The method of claim 1 wherein the cylindrical surface of said jacket is machined to remove a total thickness of at least between about and about inch of metal.

11. The method of claim 2 wherein the jacket has an initial thickness of between about 0.25 and about 1.0 inch 12. The method of claim 1 wherein the press roll body is formed from a non-weldable metallic material.

13. The method of claim 1 wherein the jacket is provided by welding the seams of a plurality of metal plates about the press roll body.

14. The method of claim 1 wherein the jacket is provided in the form of a tube by longitudinally welding a single plate about the press roll body.

References Cited UNITED STATES PATENTS 861,558 7/ 1907 Totten. 2,026,605 1/ 1936 Antisell 29-527.2 X 2,219,085 10/ 1940 Watson 29-1484 2,765,526 10/ 1956 Sparks et a1 29-5272 X 3,007,231 11/ 1961 Garver 29-1484 3,098,285 7/ 1963 Kelzenberg et al. 29-l48.4 3,156,968 11/ 1964 White 29-148.4 X

JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner US. Cl. X.R. 29-1219, 447, 527.2; 241-293 

